package Interview;

import java.util.Scanner;

/**
 * Created by loso on 2017/4/7.
 */
public class _jingdong_20170407Test2 {

    static double[] p;

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            int num = in.nextInt();
            p = new double[num];
            int linjie = (int)Math.ceil(num*0.6);

            for (int i = 0; i < num; i++) {
                p[i] = in.nextInt()/100.0;
            }
            double out = 0;
            for (int i = linjie; i <= num; i++) {
                out += solution(i,num-1);
            }
            System.out.println(out);
        }
    }

    public static double solution(int m ,int n){
        if (m > n){
            return 0;
        }
        if (m == 0){
            double o = 1;
            for (int i = 0; i <= n; i++) {
                o *= 1 - p[i];
            }
        return o;
        }
        return  p[n] * solution(m-1,n-1) + (1-p[n]) * solution(m,n-1);
    }

}
